Structural studies will be undertaken of the surface envelope glycoprotein of the human immunodeficiency virus (HIV), the etiological agent of human acquired immune deficiency syndrome (AIDS) at both the molecular and atomic levels of resolution. These studies could eventually lead to the development of agents to prevent spread of the virus, and to aid vaccine development. We have obtained a sufficient quantity of a soluble, glycosylated, highly pure, active analog of viral gp120 for structural studies. The structure of this protein (gp130) and its complexes with monoclonal antibodies will be studied by electron microscopy, x- ray diffraction and computer modeling. We will determine molecular shape and size using images of single molecules prepared by different methods and by analysis of two dimensional arrays of gp130 produced on lipid monolayers and treated carbon surfaces. We will determine conditions to produce x-ray grade crystals of gp130 and deglycosylated gp130 using a range of pH values, precipitants, ionic strengths and specific additives. When microcrystals are produced, they will be examined by electron microscopy to further determine molecular shape, and to define unit cell and packing parameters. Larger crystals will be used to determine the 3-dimensional structure of gp130. Crystals of complexes between gp130 and several monoclonal antibodies will be sought with the final goal of learning the folding of the protein backbone and the side chain locations. We will also use a recently developed computer method (PROFILE) to place the HIV gp130 in a family of folded proteins, and produce a conjectural three- dimensional model for folding of the protein backbone.